I'm assuming this question pertains to
artificial sweeteners, popular examples
being sucralose (in Equal and Splenda) and
aspartame (in Nutrasweet).

Sucralose is an indigestible compound
formed from sucrose by replacing the OH
groups on sucrose sugar molecules with chlorine
atoms. There are various
ways to perform this synthesis, but
in general it is achieved by protecting an
OH group that should be retained in the final
product, chlorinating to remove the desired
groups, then hydrolysis to remove the
protective substitute.

Aspartame is a combination of two amino
acids. Many synthesis steps are proprietary,
but some
aspects are known .
Nutrasweet is the result of fermentation and
synthesis. First, bacteria which produce
the appropriate amino acids are cultivated in
large quantities. The bacteria are allowed to
produce the amino acids until the manufacturer
decides a sufficient quantity is present. The
amino acids are then separated and dried. One of
the amino acids, phenylalanine, is then
reacted with methanol to produce and ester. The
other amino acid, aspartic acid, is then
modified (proprietary step) so it only reacts in
the intended manner. The modified acids are then
combined at elevated temperatures so they can
react. After cooling and adding a solvent, the
products of the reaction crystallize. This
compound is further reacted with acetic
acid. The final aspartame product is filtered
to remove unwanted substances.

There are, of course natural sweeteners as
well. These are also made through chemical
syntheses, but the processes are carried out by
living organisms rather than in factories.
For example, plants produce sugar (via
photosynthesis) and
stevia , while bees produce
honey .

Answer 2:

Depends on the sweetener. Sugar is processed from
a grass called sugarcane, which in turn produces
the sugar from carbon dioxide in the air and water
in the ground using sunlight for energy; this
process is called photosynthesis, and also
produces oxygen as a waste product. Other
sweeteners use different methods, but I am not
familiar with them.

Answer 3:

There are many different kinds of sweeteners,
so it depends on the exact type.
But let’s look at sucralose, since it is
the most commonly used in America.
Sucralose is produced by a multi-step
chlorination of sucrose (regular sugar).

If
you look at the atomic structure of glucose, you
will see it is made up of two six-
member rings that look like hexagons, with a lot
of OH groups coming off of the
corners. To make sucralose, all that happens is
three of those OH groups from
specific parts of the ring are removed and
replaced with Cl atoms. Of course,
chemists had to come up with a chemical reaction
which does this, and
chemical engineers had to come up with a way to
make this happen on a large
scale. Generally all of the reagents - that
is the “ingredients” of a reaction -
would be mixed together in a big container called
a reactor. The contents would
be removed and then purified so that the desired
product is isolated. Then,
after quality control and safety testing the
finished product - the sucralose - can
be delivered to people!